The War of Plagues was not a war per se but a large-scale albeit brief conflict in Antonica during the reign of Antonius Bayle IV of Qeynos. The conflict took place between Qeynos and the Bloodsaber Cult, followers of Bertoxxulous. The conflict occurred around 3100, and was reported as having lasted anywhere from "many months" to "several years." It is likely that the whole of the hostilities spanned at least two years, while the core violence was isolated to several months within a single year.
The Bloodsabers were commanded by Valdoartus Varsoon the infamous mage, and counted Lord Grimrot amongst its upper echelons of leadership. Moreover, Kane Bayle, brother to the ruler ("king") of Qeynos was later implicated as having been a conspirator in league with the Bloodsaber, a crime for which he was ultimately executed.
The Bloodsabers contaminated the Qeynosian water supply during the conflict, killing thousands of civilians, an atrocity later blamed squarely upon Varsoon the Undying.
At some point in the midst of the conflict, Varsoon demanded Qeynosians to turn over every second-born child. Apparently this caused some dissent in the ranks of the Bloodsabers, which allowed Qeynosian military forces to gain the upper hand and ultimately prevail.
According to legend the definitive battle occurred in the vicinity of the modern Qeynos Claymore Monument, the location of which heralds the spot where the Qeynos Claymore was wielded (presumably by Antonius Bayle IV) against "an evil avatar," possibly either the Avatar of Plagues (Bertoxxulous) or Varsoon himself, though Varsoon was known to have survived if he was present at the battle in question.
The legendary Bells of Vhalen, so named for the bard of the same name, was a regional alarm signal. The Tower of Vhalen was destroyed during the war when Vhalen himself used the signal bells to warn of the impending battles but "played some of the largest bard spells ever composed." It is said that Vhalen was killed while still pulling the ropes to sound the bells to warn his countrymen.